As shown in the figure, a source O of frequency 300 Hz moves towards north with a velocity of 30 m/s. A, B, C and D are four observers, each at a distance of 300 m from O. Velocity of sound is 330 m/s. As the source starts moving in the direction shown at t = 0 the frequency observed by A, B, C and D will be-

Options

A. Equal
B. 330, 300, 330, 300
C. 330, 330, 275, 250
D. 330, 300, 275, 300

Answer

D

Explanation

No dopper 's effect for observer D & B

`n_(A) = n[(vec(V) - vecV_(0))/(vecV - vecV_(s))]`
`n_(A) = 300[(330-0)/(330-30)] = 330Hz`
For C
Rest

`n_(A) = 300 [(330-0)/(330-(-30))]`
` = (330 xx 300)/(360)S`
` = 275 HZ`